Exhaust fans are often provided to suck moist air from bathrooms, smoke and steam from kitchens, and for other reasons. They are particularly useful in removing moist air from bathrooms where for example showering may take place which can create a great deal of steam. The removal of such moist air will limit the formation of mould or the like which can be a cleanliness and safety issue. Usually such bathroom fans are activated by a separate switch and can be turned on or off at will. Alternatively they may be automatically operated when there is enough moisture in the air or the bathroom is otherwise occupied. When activated the fan will suck air from the bathroom, usually at a ceiling level and then exhaust it to the outside through a dedicated exhaust duct. The fan creates a positive air flow that pushes the air out through the duct and then typically through a flapper valve, before it reaches the outside. The flapper valve typically opens by reason of the positive air pressure and then closes due to gravity.
Various types of vent structure exist to house the flapper valve at the discharge end of the duct. In general such vent structures typically include a body on the outside which covers the duct opening and prevents weather from entering backwardly through the duct. As well, typically the vent body includes a form of grill or the like to let air pass out while at the same time to keep out pests such as birds, bugs and rodents or the like from entering the building through the duct. As well, as noted above, they typically include a flapper valve to prevent the loss of air (and thus energy) out of the discharge end of the duct when the fan is not operating. Lastly they typically include some form of collar to anchor the duct in place to the body of the vent.
Although many prior designs of specialized vent bodies have been proposed in the past, in some cases roofers will cover the duct discharge end with a conventional passive roof vent. While this provides some protection for the discharge end of the duct it is generally not sufficient, in that there may be no provision of a flapper valve. Without a flapper valve this can lead to drafts in the bathroom and a loss of energy. The flapper doesn't allow the moist air to freeze. In a prior patent to Ward (U.S. Pat. No. 8,205,401), an attempt is made to provide a flapper adaptor so that a conventional passive roof vent can be adapted to perform as an end cover for a bathroom or forced air duct. In Ward there is provided a device which includes a separate flapper adaptor unit which defines a discharge chimney that extends up above the roof surface. A flapper valve hinged at an angle and attached at one end is provided on the top of the chimney. The flapper adaptor is provided with upwardly reaching fingers to allow it to be placed inside of the vent opening of the vent body and the grab the top edge of the same to keep it in place. Below a separate collar adaptor, with various collar diameters for attaching to different sizes of ducts, is provided. The separate collar adaptor, the flapper adaptor and the body of the vent are then combined together to form a complete unit.
While providing a flapper valve option for the specific roof vent design shown there are certain problems associated with this prior design. The design involves three separate components each of which must be positioned correctly to ensure the combination functions as required. The use of separate components leads to the risks of installer error and leaks. As well the flapper adaptor includes a raised collar which has an angled top on which the flapper valve sits. To ensure proper functioning of the flapper valve the valve must be oriented correctly, relative to the roof incline, to prevent the flapper valve from being too hard to lift. As well the flapper valve stands proud of the roof deck meaning that the body of the vent must be large enough to accommodate the range of travel of the flapper valve when it opens and closes and the adaptor fingers will only latch onto a vent having a vent opening as shown in the drawings. Thus this prior adaptor combination is limited to being used with a roof vent the same as or substantially the same as what is shown.
Other types of flapper valves provided in the prior art include:                U.S. Pat. No. 4,144,802;        U.S. Pat. No. 4,432,273;        U.S. Pat. No. 4,593,504;        U.S. Pat. No. 5,662,522;        U.S. Pat. No. 5,749,780;        Canadian Patent No. 2,696,466.        
What is desired is a simple and reliable universal adaptor that can be used in association with many different types and styles of roof vent bodies. A universal adaptor is desirable as opposed to one which can only be used in association with one specific roof vent body as taught in the prior art. Preferably such a universal device would be simple to minimize the risk of incorrect installation and in-expensive to make and use. Preferably such a product can be installed from either side of the roof sheathing. Such a design is also preferably reliable. Most preferable such a device would be made from a durable molded plastic and would be compatible with a wide range of vent bodies.